Platelet Response to Clopidogrel Is Attenuated in Diabetic Patients Undergoing Coronary Stent Implantation

Type 2 diabetes is accompanied by platelet function disorders leading to an accelerated process of atherosclerosis and increased risk for atherothrombotic complications (1–4). Previous data (5,6) suggest a worse outcome for diabetic patients after acute coronary events. Recently, a high variability of response to clopidogrel measured by platelet function tests has been reported (7) among patients with percutaneous coronary intervention (PCI), and hyporesponsiveness to clopidogrel has been considered to influence cardiac outcome in these patients (8–10). Impaired response to antiplatelet therapy in diabetic patients has been reported (11,12) in small patient collectives. However, little is known about the effects of type 2 diabetes on response after a 600-mg clopidogrel loading dose in large unselected cohorts of patients with symptomatic coronary artery disease (CAD). Type 2 diabetic and nondiabetic patients treated by coronary stenting for symptomatic CAD were consecutively enrolled in this study. The protocol was approved by the local ethics committee, and signed informed consent was obtained from all patients. Patients with known platelet function disorders, thrombocytopenia (<105 cells/mm3), or any contraindications against clopidogrel were excluded. A loading dose of 600 mg clopidogrel was given to all patients before PCI, followed by 75 mg every day. All patients received a daily dose of 100 mg aspirin before PCI. A standard dose of heparin was given to all patients immediately before PCI unless there were no contraindications. Type 2 diabetes was defined according to the recommendations of the American Diabetes Association (13). Patient blood was collected ≥6 h (46.6 ± 99.3 h) after administration of 600 mg clopidogrel, when maximum platelet inhibition was expected (14). Among the subgroups of diabetic …